Frequently Asked Deck Buildings Questions (continued)

So, since you will be going below the frost line, I would say mount your ledger board if the posts are 6x6's. If the posts on the upper deck are only 4x4's (at that height they ought to be 6x6) then just make it freestanding and dig those few more holes.

Attaching Deck to House

I am replacing my deck which was attached directly to the house with each joist inserted into an 8" cutout in the brick; so that instead of being supported by a ledger attached to the house, the deck is supported by the house itself. The deck is 12x10 with 3 brick pillars supporting the side of the deck opposite the house. My question should I rebuild the deck by attaching a new ledger to the house or is the deck more solid as is, resting on the house.

I think either will work, but since the cutouts in the brick are there... use them. It is easier and provides better support than a ledger added to the wall would.

Cantilever Deck Joists

Generally you can go a third of the distance cantilevered.  I your case, with an 18 ft board, that would be 6 feet.    But when you start getting way out there, I am not sure I like that rule. While 5 ft is probably do-able there may  be more bounce than you would like. I wouldn't go the whole 5 feet unless you absolutely needed to.

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If I were building the deck, I would place supports at the 9 ft position as well as the 18ft position and get as rock hard deck as possible with 2x10s.

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The one third, two thirds rule does not take in consideration of the up lift which is caused by weight out on the cantilever. If the joist are under the house wall is one thing but if there attached with joist hanger there is nothing holding the joist down. Joist hangers are designed for downward pressure not to hold them down. If you can handle the upward lift at the than I would double up each joist and have solid blocking on the outer beam. Because when joists bend they want to twist.

Cantilevers & Circular Deck Design

We are thinking of building a deck on that would be a part of a 25 foot radius semicircle attached to the rear of our home. I've looked in a few books with no luck for design tips. I get all wobbly when I think of the structural design of a deck out by the edge. I have a few ?s.  Anyone seen a design like this, how to address the edge of the structure? Published?

How far could I cantilever the decking beyond the rim?

You can cantilever out on a joist, about 1/3 the total length of the joist. But don't get carried away. 3 ft should be max on 2x6 joists. But what you can do, is use beams along the perimeter. With a main beam 12 ft out from the house and a smaller one 22-24 ft out, you can connect the house to the main beam and the main beam to the outer beam with beams. Then the joists will have something to rest on at about their outer edges.

Family Handyman magazine ran a how-to about 11/2 years ago with some good diagrams. Maybe you can find an old copy at your library.